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Authigenic clays in close textural relation to carbonate fluorapatite within finely laminated phosphate stromatolites of Upper Jurassic age have been studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Stromatolite laminae consist of hexagonal prisms of francolite (sizes ranging between 0·1 and 1 μm) that are surrounded by poorly crystalline smectite and amorphous Fe–Si–Al oxyhydroxides. Microanalyses show that smectite is Fe rich, with highly variable composition, particularly regarding Fe and Si contents. Smectite has significant beidellitic, montmorillonitic and non-tronitic substitutions. Although the lack of fringe contrast in some areas adjacent to the smectite packets with 1·0–1·3 nm spacing is due to differences in orientation of layers, textural and analytical data clearly indicate the presence of Fe–Si–Al amorphous phases intimately intergrown with smectite. The occurrence of poorly crystalline smectite and associated amorphous phases within microbially precipitated stromatolite laminae, both as envelopes around, and as pore-fillings between extremely small calcium phosphate crystals, demonstrates authigenic smectite growth from a precursor Fe–Si–Al amorphous material. This material is formed in close association with a phosphate-rich precursor. The textural and structural relations, the preservation of chemical precursors of glauconite such as nontronitic montmorillonite, and the presence of Fe–Si–Al amorphous mineral phases, imply crystallization of the observed crystalline phases from synsedimentary (bacterially precipitated) amorphous precursors during early diagenesis in postoxic environments. Carbonate fluorapatite was the first phase to crystallize from the primary gel; smectite and associated amorphous Fe–Si–Al oxyhydroxides were the residual material of the crystallization process. The slow rate of transformation (at low temperatures) from Fe–Si–Al-rich gels to smectite, explains the textural relations between the poorly crystalline phases and the phosphate crystals, as well as the preservation of amorphous substances in relation to clays. Authigenic smectite represents the first step in glauconitization. 相似文献
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Jeffrey Chiarenzelli Robin Lock Carol Cady Adria Bregani Benn Whitney 《Environmental Earth Sciences》2012,67(1):189-204
Water from four north-flowing rivers (Oswegatchie, Grasse, Raquette, and West Branch of the St. Regis) traversing three distinct geologic terranes (Adirondack Highlands, Adirondack Lowlands, St. Lawrence Valley), originating in the acidified northern Adirondack region, display rapid spatial changes in downriver multi-element chemistry and physical parameters. Downriver, most soluble elements increase (Ba, Ca, Cu, K, Mg, Na, Rb, S, and Sr) while statistically significant decreases in insoluble elements (Al, Ce, Dy, Er, Fe, Gd, La, Mn, Nd, Pr, and Y) also occur. Lithium, Si, and Zr did not show a consistent increasing or decreasing trend. Concentrations of most elements measured on June 5, 2008 were greater than 7?weeks later; however, greater discharge and lower pH enhanced Al concentrations occurred during the later sampling date. Elemental ratios track changes in lithology, anthropogenic influence, and pH. The Raquette River shows the least variation in elemental concentrations because of storage in numerous hydropower reservoirs and has non-detectable concentrations of some redox sensitive elements such as Co, Ni, and V. Oswegatchie tributaries display similar geochemical trends dependent upon their location and local bedrock and show geochemical trends along the trunks of major rivers that are also evident in smaller drainage basins. Comparison with analytical results from the Western Adirondack Stream Survey also indicates acidification is prevalent in the Adirondack Highlands, particularly in the Oswegatchie headwaters during periods of high flow, but acidity is rapidly buffered downriver due to interaction with marble in the Adirondack Lowlands. 相似文献
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《Applied Geochemistry》2005,20(7):1391-1408
Surface water samples from the St. Lawrence River were collected in order to study the processes controlling minor and trace elements concentrations (Al, Fe, Mn, Cd, Co, Cu, Ni and Zn), and to construct mass balances allowing estimates of the relative importance of their natural and anthropogenic sources. The two major water inputs, the upper St. Lawrence River, which drains waters originating from the Lake Ontario, and the Ottawa River were collected fortnightly over 18 months. In addition, other tributaries were sampled during the spring floods. The output was monitored near Quebec City at the river mouth weekly between 1995 and 1999. Dissolved metal concentrations in the upper St. Lawrence River carbonated waters were lower than in the acidic waters of the tributaries draining the crystalline rocks of the Canadian shield and the forest cover. Biogeochemical and hydrodynamic processes occurring in Lake Ontario drive the seasonal variations observed in the upper St. Lawrence River. Biogeochemical processes relate to biological uptake, regeneration of organic matter (for Cd and Zn) and oxyhydroxide formation (for Mn and Fe), while hydrodynamic processes mainly concern the seasonal change in vertical stratification (for Cd, Mn, and Zn). In the Ottawa River, the main tributary, oxyhydroxide formation in summer governs seasonal patterns of Al, Fe, Mn, Cd, Co and Zn. The downstream section of the St. Lawrence River is a transit zone in which seasonal variations are mainly driven by the mixing of the different water masses and the large input of suspended particulate matter from erosion. The budget of all dissolved elements, except Fe and Zn, was balanced, as the budget of particulate elements (except Cd and Zn). The main sources of metals to the St. Lawrence River are erosion and inputs from tributaries and Lake Ontario. Direct anthropogenic discharges into the river accounted for less than 5% of the load, except for Cd (10%) and Zn (21%). The fluxes in transfer of dissolved Cd, Co, Cu and Zn species from the river to the lower St. Lawrence estuary were equal to corresponding fluxes calculated for Quebec City since the distributions of dissolved concentrations of these metals versus salinity were conservative. For Fe, the curvature of the dilution line obtained suggests that dissolved species were removed during early mixing. 相似文献
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Study of Carbon‐Bearing Particles in Ascending Geogas Flows in the Dongshengmiao Polymetallic Pyrite Deposit,Inner Mongolia,China 
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下载免费PDF全文 Samples of ascending geogas flow particles were collected on to SiN grids directly in the Quaternary sediments overlying the Dongshengmiao polymetallic pyrite deposit, China. Corresponding soil samples were collected in the surface of Dongshengmiao district at the same time. After pretreatment, these SiN grid samples were analyzed by transmission electron microscopy. The tests focused on the characteristics of particles including size, shape, chemical composition, structure and association. The results show that there are numerous carbon‐bearing particles in particulate samples of the ascending geogas flow. The particles contain organic matter, carbonate or carbonate mixed with other minerals. These carbon‐bearing particles generally contain metallic elements like Fe/Zn/Au/Cu/Pb. However, all of the soil particles do not contain elemental C and only consist of common elements (O, Na, Mg, Al, Si, Ca, Ti) just like the composition of earth crust. Through a comparison between the particles from different sources, the carbon‐bearing particles were found to come only from the deep earth and carried useful information about concealed deposits as they pass through the deep‐seated orebodies. Given the influences of organic matter on mineralization, the carbon‐bearing particle may provide information on the deposit genesis. Combining the use of geogas particle for prospecting with characteristics of large depth, and the carbon‐bearing materials' close spatial and genetic relationship with orebodies, we propose a new prospecting method based on the characteristics of carbon‐bearing particles, including morphology, size, chemical component and ultra‐microstructure. This approach could be applied to the exploration of deposits deep in the earth and abundant in carbon‐bearing matter. This approach can provide efficient and effective deposit exploration. 相似文献
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Apatites occurring in lateritic residues derived from high-grade metamorphic rocks from Sri Lanka are hydroxy-apatite as indicated by EPMA and XRD. Weathered phosphates and weathered crystalline products are composed of carbonate fluorapatite, crandallite, wardite, fluellite, kaolinite, goethite and gibbsite. EDAX, DTA and SIMS show the presence of amorphous materials, such as oxides of Fe, Al, Si, Al+Si, and S, on the surface of weathered phosphate. Using SEM, TEM, EDAX and electron diffraction techniques, the presence of these amorphous and crystalline materials with several transitions has been clearly identified in weathered phosphate. Recrystallization of phosphate occurred during weathering by dissolution, nucleation and precipitation. The lattice images of hydroxyapatite are gradually increased from 8.3-A basal spacings by weathering, and form mosaic bound fragments. Chondrite-, shale- and phosphorite concretion-normalized REE patterns of these apatites, known to have sedimentary origins, suggest enrichment and remobilisation during post-depositional reworking. 相似文献
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Subsurface waters circulating in an unpolluted soil of a planosolic horizon (Massif Central, France) were studied in order to determine their physico-chemical characteristics. Three water sampling sites were chosen along a toposequence. For each site, two piezometers were placed above and in the gravelly and concretion-rich horizon (Fe- and Mn- oxyhydroxides). Concentrations of major-, minor- (cations, anions, Fe, Mn, P and Si) and trace elements (Al, Ba, Cd, Co, Cr, Cu, Ni, Pb, Rb, Sr, Zn and U) were monitored on bulk and filtered water (0.45 μm) to study both the particulate and the dissolved components, from 2004 to 2006, during the soil saturation period (i.e., from November to May). Chemical characteristics of soil solutions provide evidence for various chemical water compositions and for temporal variations of water quality, revealing that the hydrodynamic and chemical reactivity in the solution is different for the three sites. Calculations of pe values indicate a range of redox state of the soil solutions. The pe ranges are different for each piezometer but correspond to anoxic solution. For all piezometers, distribution between the dissolved and the particulate fraction and correlations between the various elements in the soil solutions indicate that: (i) Al and Fe show similar behaviour, (ii) Al is mainly present as oxyhydroxides and (iii) some trace metals are mainly associated with particles which have a mixed nature. The impact of a concretion-rich horizon is noticed both on the nature of particles and on the speciation of trace metals and could be explained by the hydrodynamic and chemical reactivity of the circulating solution. Very few correlations exist between elements in the dissolved phase. 相似文献
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Sixteen elements (Ca, K, Mg, Na, Al, Fe, Mn, P, Co, Cu, Li, Ni, Rb, Sr, Ti, Zn, determined by atomic absorption) were identified in 453 pumice fragments recovered from Holocene strandplains in southeast Queensland and New South Wales. Eight pumice groups and 13 subgroups are recognised by numerical analysis. Some pumices record known eruptions. Others come from known centres in Tonga and Vanuatu. Several pumice eruptions have occurred from some centres, but there are instances of single episodes. The numerical analyses, combined with carbon dating and soil identification, identify marker horizons in the development of the strandplains. These horizons provide a time‐scale for soil development. Pumice that occurs in middens has an archaeological value. Coke was found with recent pumice. It conveniently identifies the modern industrial age. 相似文献
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PIERRE ANTOINE DENIS-DIDIER ROUSSEAU JEAN-PIERRE LAUTRIDOU CHRISTINE HATTé 《Boreas: An International Journal of Quaternary Research》1999,28(4):551-563
The loess series at St. Pierre-les-Elbeuf and St. Sauflieu are key successions for the western European Quaternary stratigraphy. The present study proposes a detailed record of the last interglacial-glacial climatic cycle at St. Pierre and its integration into the synthetic pedosedimentary record of north-western France using detailed correlations with the type sections of St. Sauflieu and Achenheim. Finally, comparisons with the marine isotope, Greenland GRIP chronologies and dust records are proposed. At St. Pierre, the pedostratigraphic and sedimentological analyses (total iron, organic matter, carbonate, grain size), in association with low field magnetic susceptibility measurements, demonstrate that this loess succession records the major climatic events of the Upper Pleistocene. The basal soil complex at St. Pierre is similar to those from the main successions of North (St. Sauflieu) or Northeast France (Achenheim). It shows a Bt horizon of brown leached soil, a deeply reworked grey forest soil and two isohumic steppe soils separated by a non-calcareous loess layer. This loess level corresponds to the first aeolian event clearly observed in the succession and can be correlated with Marker II of the Central European stratigraphy located around the marine isotope stage (MIS) 5/4 boundary. The main aeolian sedimentation starts after the soil complex and ends with the top soil (brown leached soil). Finally, a good parallel is observed between the strongest peaks of the dust records of the ice cores and the main period of loess deposition in St Pierre-lès-Elbeuf occurring during MIS 2. 相似文献
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Manganese nodules and manganese carbonate concretions occur in the upper 10–15 cm of the Recent sediments of Loch Fyne, Argyllshire in water depths of 180–200 m. The nodules are spherical, a few mm to 3 cm in diameter, and consist of a black, Mn-rich core and a thin, red, Fe-rich rim. The carbonate occurs as irregular concretions, 0.5–8 cm in size, and as a cement in irregular nodule and shell fragment aggregates. It partially replaces some nodule material and clastic silicate inclusions, but does not affect aragonitic and calcitic shell fragments.The nodules are approximately 75% pure oxides and contain 30% Mn and 4% Fe. In the cores, the principal mineral phase is todorokite, with a Mn/Fe ratio of 17. The rim consists of X-ray amorphous Fe and Mn oxides with a Mn/Fe ratio of 0.66. The cores are enriched, relative to Al, in K, Ba, Co, Mo, Ni and Sr while the rims contain more P, Ti, As, Pb, Y and Zn.The manganese carbonate has the composition (Mn47.7 Ca45.1 Mg7.2) CO3. Apart from Cu, all minor elements are excluded from significant substitution in the carbonate lattice.Manganese nodules and carbonates form diagenetically within the Recent sediments of Loch Fyne. This accounts for the high Mn/Fe ratios in the oxide phases and the abundance of manganese carbonate concretions. Mn concentrations in the interstitial waters of sediment cores are high (ca. 10 ppm) as also, by inference, are the dissolved carbonate concentrations. 相似文献
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New insights into the 3D structure, composition and origin of the Mt Ashmore dome, west Bonaparte Basin, Timor Sea, are enabled by reprocessed seismic-reflection data and by optical microscopic, X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) analyses of drill cuttings. The structural dome, located below a major pre-Oligocene post-Late Eocene unconformity and above a ～6 km-deep-seated basement high indicated by marked gravity and magnetic anomalies, displays chaotic deformation at its core and a centripetal kinematic deformation pattern. A study of drill cuttings of Lower Oligocene to Lower Jurassic sedimentary rocks intersected by the Mt Ashmore 1B petroleum-exploration well reveals microbrecciation and extreme comminution and flow-textured fluidisation of altered sedimentary material. The microbreccia is dominated by aggregates of poorly diffracting micrometre to tens of micrometres-scale to sub-millimetre particles, including relic subplanar fractured quartz grains, carbonate, barite, apatite and K-feldspar. A similar assemblage occurs in fragments in basal Oligocene sediments, probably derived from the eroded top section of the dome, which protrudes above the unconformity. SEM coupled with EDS show the micrometre to tens of micrometres-scale particles are characterised by very low totals and non-stoichiometric compositions, including particles dominated by Si, Al–Si, Si–Ca–Al, Si–Al–Ca, Si–Mg, Fe–Mg–Ca, Fe–Mg and carbonate. XRD analysis identifies a high proportion of amorphous poorly diffracting material. TEM indicates internally heterogeneous, fragmented and recrystallised structure of the amorphous grains, which accounts for the low totals in terms of the high-volatile and porous nature of the particles. Another factor for the low totals is the uneven thin-section surfaces which affect the totals. No volcanic material or evaporites were encountered in the drillcore, militating against interpretations of the structure in terms of magmatic intrusion or salt diapirism. Such models are also inconsistent with the strong gravity and magnetic anomalies, which signify a basement high below the dome. An interpretation of the dome in terms of a central rebound uplift of an impact structure can not be proven due to the lack of shock metamorphic effects such as planar deformation features, impact melt or coesite. However, an impact model is consistent with the chaotic structure of the domal core, centripetal sense of deformation, microbrecciation, comminution and fluidisation of the Triassic to Eocene rocks. In this respect, an analogy can be drawn between the Mt Ashmore structural dome and likely but unproven impact structures formed in volatile (H2O, CO2)-rich sediments where shock is attenuated by high volatile pressure, such as Upheaval Dome, Utah. In terms of an impact hypothesis the Mt Ashmore dome is contemporaneous with a Late Eocene impact cluster (Popigai: D = 100 km, 35.7 ± 0.2 Ma; Chesapeake Bay: D = 85 km, 35.3 ± 0.1 Ma). 相似文献
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Assessment of cement’s dust impact on the soil using principal component analysis and GIS 总被引：2，自引：1，他引：1
Z. Zerrouqi M. Sbaa Ph.D. M. Oujidi Ph.D. M. Elkharmouz S. Bengamra A. Zerrouqi 《International Journal of Environmental Science and Technology》2008,5(1):125-134
To evaluate the impact of the cement’s dust emitted by the eastern Moroccan cement factory (Oujda Holcim) and deposited on the soil of the Ain Lahjar commune, 58 samples of soil were collected around the factory on a radius of 3 km approximately. The physicochemical analyses of the upper 3 cm of the soil surface samples correspond to the pH, electrical conductivity, the chlorides and the oxides of Ca, Al, Fe, K, Mn, S and Si which were analyzed by the fluorescence of X-rays. The preliminary results demonstrate that this dust are especially basic and contain a high free lime (43% CaO). The principal component analysis (applied on the 58 samples of soil) allows deducting that the free lime and the sulfur oxide are the tracer elements of this form of pollution. Furthermore, the spatial projection of the factor scores of the principal component analysis using the geographical information system permits to determine the spatial distribution of more polluted areas of soils as well as to estimate their surface (63.3% of the survey zone). 相似文献
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Iron silicate minerals are a significant component of sedimentary systems but their modes of formation remain controversial. Our analysis of published data identifies end‐member compositions and mixtures and allows us to recognize controls of formation of different mineral species. The compositional fields of glaucony, Fe‐illite, Fe–Al smectites are determined in the M+/4Si vs. Fe/Sum of octahedral cations (M+ = interlayer charge). Solid solutions could exist between these phases. The Fe–Al and Fe‐rich clay minerals form two distinct solid solutions. The earliest phases to be formed are Fe–Al smectites or berthierine depending on the sedimentation rate. Reductive microsystems appear in the vicinity of organic debris in unconsolidated sediments. The Fe is incorporated first in pyrite and then in silicates after oxidation. Potassium ions diffuse from the sea‐water–sediment interface. If not interrupted, the diffusion process is active until reaction completion is reached, i.e. formation of Fe‐illite or glauconite or a mineral assemblage (berthierine–nontronite) according to the available Al ion amounts in the microsystem. Mixed‐layer minerals are formed when the diffusion process is interrupted because of sedimentation, compaction or cementation. Despite the common belief of their value as palaeoenvironment indicators, these minerals can form in a variety of environments and over a period of millions of years during sediment burial. 相似文献
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Sarwono Hardjowigeno Dr. 《GeoJournal》1992,28(2):131-138
The properties and development of soils derived from pumiceous tuff of the 1883 Krakatau eruption were studied on Rakata island during 1983 and 1989. Field observations on soil profiles of different altitude and topography, and laboratory data, revealed that in a period of 100 years soil development has resulted in the formation of a pronounced A-horizon of 5–15 cm thickness underlaying an AC or weak B horizon. Solum development commonly reaches to a depth of approximately 25 cm. The dominant process of soil formation was decomposition of organic matter and aggregation of soil particles in the surface horizon. There was also a slight indication of iron and fine clay translocation but base cations were accumulating in the surface horizon. Soils at 600 m altitude and higher commonly contained lower base saturation, pH, and weatherable minerals, and higher exchangeable A1 and H than those at lower altitudes. The dominant clay minerals were montmorillonite, kaolinite and other layer silicate clays. It is believed that the clays were not formed pedogenically. Some pedons at higher altitudes were dominated by amorphous material in the clay fraction.Presented at the XVII Pacific Science Congress, May 27–June 2, 1991. Honolulu, Hawaii, USA 相似文献
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《Chemie der Erde / Geochemistry》2021,81(4):125770
The distribution of gold in the weathering blanket at the Belikombone gold prospect in east Cameroon provides insights into gold mobility in the secondary environment and in tropical terrains worldwide. Both gridline-controlled sampling of topsoil (surface samples) and sampling of various layers in pits are used and the gold assay for each sample determined by NiS fire assay with ICP-AES finish. One hundred and thirty-two (132) surface samples and a total of 206 samples from 19 exploration pits were analyzed. The results from the topsoil samples show an anomaly with the highest Au concentration at 5.9 mgkg−1. The mineralization corridor follows a NE-SW trend. The horizons within the pits range from sap rock at the base, through saprolite, rubble layer rich in relict quartz material to a ferruginous loose layer at the top although some horizons are missing in some pits. All the layers contain gold and the highest concentration in the sap rock horizon is 3.4 mgkg−1 while the rubble layer has a gold high of 6.1 mgkg−1. The individual soil horizons show no systematic gold trends and given the presence of gold in all layers, the patterns point towards supergene dissolution and redistribution of gold. Gold enrichment within the upper horizons in the weathering blanket is attributed to sequestration by Fe oxides of chemically remobilized gold. However, the high gold content within the sap rock and saprolite layers suggests that migration of gold in the particulate form supersedes chemical gold redistribution. Particulate gold obtained by panning samples from the pits varies in shape from euhedral, elongated to irregular. Electron microprobe analysis on the grains record high contents of gold in the rim zones (90.0 to 99.8 wt%). The cores are relatively rich in Ag (12.6 to 14.2 wt%) while the rims are poor in Ag. The low Ag content in the rims is attributed to the preferential leaching of Ag. The soil pH value in this area varies between 3.6 and 7.3. Under such acidic to near neutral conditions, bisulfide and thiosulfate ions can dissolve and transport Au and Ag to be precipitated under surficial conditions creating authigenic Au haloes especially in the saprolite and sap rock layers. Such pH values together with oxidizing Eh conditions explain the solubility of gold in the area. These results are important for geochemical exploration of gold in tropical terrains, and confirm previous studies. 相似文献
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James M. Kaste Benjamin C. Bostick Eiliv Steinnes 《Geochimica et cosmochimica acta》2011,75(6):1642-1661
High concentrations of metals in organic matter can inhibit decomposition and limit nutrient availability in ecosystems, but the long-term fate of metals bound to forest litter is poorly understood. Controlled experiments indicate that during the first few years of litter decay, Al, Fe, Pb, and other metals that form stable complexes with organic matter are naturally enriched by several hundred percent as carbon is oxidized. The transformation of fresh litter to humus takes decades, however, such that current datasets describing the accumulation and release of metals in decomposing organic matter are timescale limited. Here we use atmospheric 210Pb to quantify the fate of metals in canopy-derived litter during burial and decay in coniferous forests in New England and Norway where decomposition rates are slow and physical soil mixing is minimal. We measure 210Pb inventories in the O horizon and mineral soil and calculate a 60-630 year timescale for the production of mobile organo-metallic colloids from the decomposition of fresh forest detritus. This production rate is slowest at our highest elevation (∼1000 m) and highest latitude sites (>63°N) where decomposition rates are expected to be low.We calculate soil layer ages by assuming a constant supply of atmospheric 210Pb and find that they are consistent with the distribution of geochemical tracers from weapons fallout, air pollution, and a direct 207Pb application at one site. By quantifying a gradient of organic matter ages with depth in the O horizon, we describe the accumulation and loss of metals in the soil profile as organic matter transforms from fresh litter to humus. While decomposition experiments predict that Al and Fe concentrations increase during the initial few years of decay, we show here that these metals continue to accumulate in humus for decades, and that enrichment occurs at a rate higher than can be explained by quantitative retention during decomposition alone. Acid extractable Al and Fe concentrations are higher in the humus layer of the O horizon than in the mineral soil immediately beneath this layer: it is therefore unlikely that physical soil mixing introduces significant Al and Fe to humus. This continuous enrichment of Al and Fe over time may best be explained by the recent suggestion that metals are mined from deeper horizons and brought into the O horizon via mycorrhizal plants. In sharp contrast to Al and Fe, we find that Mn concentrations in decomposing litter layers decrease exponentially with age, presumably because of leaching or rapid uptake, which may explain the low levels of acid extractable Mn in the mineral soil. This study quantifies how metals are enriched and lost in decomposing organic matter over a longer timescale than previous studies have been able to characterize. We also put new limits on the rate at which metals in litter become mobile organo-metallic complexes that can migrate to deeper soil horizons or surface waters. 相似文献